Filters for use in water purifiers or water treatment equipment serve to filter off impurities contained in water or other liquid passing therethrough, thereby extracting only pure water or liquid.
When repeatedly carrying out the above described filtering operation, impurities are continuously adhered to and accumulated on the surface of a filter, or slight damage to the filter occurs, which causes deterioration in the capability of the filter as time passes. For this reason, periodically replacing the filter is essential to maintain uniform water purification or water treatment quality.
To this end, standardized filter cartridges have been developed. Such a filter cartridge in which a filter is accommodated is coupled to a filter holder when in use and then, after the lifespan of the filter terminates, the filter cartridge is separated from the filter holder so as to be replaced with a new filter cartridge in a simplified manner.
FIGS. 5 and 6 illustrate a known conventional filter cartridge, in which a multiply folded membrane filter 3 is interposed between disc-shaped holders 2 and a core 4 is centered in the membrane filter 3.
In the above described conventional filter cartridge, to increase a treatment capacity per hour, the membrane filter 3 has a multiply folded shape suitable to achieve an increased surface area.
As illustrated in FIG. 6, the membrane filter 3 of the conventional filter cartridge is fabricated by folding a flat planar membrane multiple times in zigzag and then, bonding both ends of the membrane to each other. In this case, a resulting bonded portion 5 is oriented such that a tip thereof faces outward of the filter cartridge.
In operation of the conventional filter cartridge having the above described configuration, raw water, which has been introduced into the filter cartridge through a water inlet hole 9, is filtered by the filter 3 while moving through the core 4, whereby purified water is discharged from the filter cartridge.
In this case, while passing through the filter 3, some of the raw water must pass through the bonded portion 5 as well as the surface of the filter. However, the bonded portion 5 may be contaminated with fine dust particles or impurities that have been generated during manufacture of the filter cartridge, which causes the impurities to be unintentionally contained in the purified water to be transmitted to a user.
In addition, since only one filter 3 is used to purify water, water purifying capability may not be sufficient.